1. Field of the Invention
This invention relates to side-chain crystallizable polymers, and particularly to inherently radiopaque side-chain crystallizable polymers useful in medical applications.
2. Description of the Related Art
Polymeric materials are widely used in numerous applications. For example, therapeutic embolization is the selective blockage of blood vessels or diseased vascular structures. Examples of polymeric embolotherapy devices and reagents include embolic coils, gel foams, glues, and particulate polymeric embolic agents used, for example, to control bleeding, prevent blood loss prior to or during a surgical procedure, restrict or block blood supply to tumors and vascular malformations, e.g., for uterine fibroids, tumors (i.e., chemo-embolization), hemorrhage (e.g., during trauma with bleeding) and arteriovenous malformations, fistulas (e.g., AVF's) and aneurysms.
Polymeric liquid embolic agents include precipitative and reactive systems. For example, in a precipitative system, a polymer may be dissolved in a biologically acceptable solvent that dissipates upon vascular delivery, leaving the polymer to precipitate in situ. Reactive systems include cyanoacrylate systems in which, e.g., a liquid monomeric and/or oligomeric cyanoacrylate mixture is introduced to the vascular site through a catheter and polymerized in situ. In this system, polymerization is initiated by the available water in the blood.
A number of technological applications involve the use of a polymer that undergoes a transition upon a change in temperature. For example, in the medical field, one way to introduce a solid polymer into a particular body region is to heat the polymer into a flowable state, then inject the polymer into the region and allow it to cool and solidify. U.S. Pat. No. 5,469,867 discloses side-chain crystallizable polymers that are said to be useful for occluding channels in a living mammal. Such polymers are said to be designed such that they can be melted so that they are flowable slightly above body temperature but solidify when cooled to body temperature.